Pulse generating direct-current measuring bridges

ABSTRACT

A measuring bridge regulator in which the bridge diagonal circuit has a capacitor, and also, in parallel with the capacitor, a break-through device and the primary winding of an impulse transformer. When the bridge is balanced, there is no charge on the capacitor. When imbalance occurs, a charge builds up in the capacitor, and when the difference in potential in the bridge circuit becomes sufficiently great to cause the breakthrough device to fire, the capacitor discharges through the primary of the impulse transformer. This creates a pulse in the secondary winding of the transformer, which pulse operates a relay to provide power for an adjusting motor in a direction to tend to restore balance to the measuring bridge.

United States Patent Albrecht et al. 51 Oct. 17, 1972 [54] PULSEGENERATING DIRECT- 2,987,713 6/1961 Bagno ..323/75 N CURRENT MEASURINGBRIDGES 3,075,086 l/l963 Mussard ..323/75 E 3,286,144 11/1966 Hill..3l8/674 X [72] Invemms' 113;? ff "',1 ;1'";,f;; 3,398,359 8/1968 Weber..323/75 N Braunschweig, both of Germany Primary Examiner-A. D. Pellinen[73] Assignee: Rollei-Werke Franks & Heidecke, Attomey C-hafles ShepardBraunschweig, Germany [22] Filed: July 1, 1971 [57] ABSTRACT [21] Appl.No.: 158,956 A measuring bridge regulator in which the bridge diagonalcircuit has a capacitor, and also, in parallel with the capacitor, abreak-throu h device and the [30] Fomgn Apphcauon Pnomy Data primarywinding of an impulse tran former. When the y 7, 1970 Germany 20 37518-2 bridge is balanced, there is no charge on the capacitor. Whenimbalance occurs, a charge builds up in the U-S- N capacitor and whenthe difference in potential in the [51] Int. Cl. ..G05b ll/0l bridgecircuit becomes ffi i tl great to cause the [58] Field of Search..318/609, 610, 672, 674; break through device to fire, the capacitordischarges 323/75 75 N through the primary of the impulse transformer.This creates a pulse in the secondary winding of the trans- [56]References C'ted former, which pulse operates a relay to provide powerUNITED STATES PATENTS for an adjusting motor in a direction to tend torestore balance to the measuring bridge. 2,860,298 11/1958 Carlson..318/674 X 3,423,602 l/l969 Louis ..323/75 N 7 Claims, 2 DrawingFigures PATENTEDncT 17 I972 FIGI ' Fig.2

cgsa I BACKGROUND OF THE INVENTION present invention relates. Suchbridges operate on the zero compensation principle. With certain knownbridges, the follow-up of the regulator is effected intermittently andat certain intervals of time. With regulators of this kind, the durationof the impulses and the time intervals between them are such that theregulating speed is adapted to the retardation to which the regulatingprocess is subject, in order to avoid oscillation. When the controlmagnitudes become altered, the measuring bridge is detuned or broughtinto a state of imbalance, and this imbalance is utilized to bring aboutthe follow-up or readjustment of the control magnitudes. With highlyretarded control processes, a long time elapses before the adjustment ofthe controlled magnitude overcomes the imbalance. To avoidover-compensation, therefore, the control process set up by the bridgemust be retarded, or sub-divided into individual steps, to the extentnecessitated by the inertia of the controlled process. In the past, usehas been made of interval switches by which the measuring circuit isswitched on and off at certain intervals of time. When the bridge isunbalanced or detuned, therefore, the regulation is effected in smalland short steps, and is retarded by the intervals between these steps tosuch an extent that is adapted to the inertia of the regulated process.The switching times of the interval switch must be selected to ensurethat over-regulation is avoided.

An object of the present invention is to provide an efficient andsatisfactory regulator which operates without moving parts and withoutneeding an interval switching device such as commonly used in the pastas above mentioned, but which nevertheless generates control impulses,the pulse train or the interval between pulses being automaticallyadapted to the degree of deviation in the measurement, i.e., the amountof the imbalance or the degree of deviation from the desired balancedstate.

Another object of the invention is the provision of a regulating devicewhich, in the absence of imbalance, will emit no impulses, and in whichthe timing of impulses in the case of imbalance is proportional to thedegree of imbalance, the control impulses being emitted at a faster ratethe greater the degree of imbalance or detuning.

A further object of the invention is the provision of a regulator inwhich the control impulses are produced to the same intensity and withthe same duration, and 'are also produced selectively with regard toregulation in a forward or reverse direction.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 of the drawing is a wiringdiagram schematically illustrating the circuitry of a preferredembodiment of the present invention.

FIG. 2 is a wiring diagram corresponding to a fragment of FIG. 1,illustrating a modification using a glow lamp in place of the diacillustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 theelectrical measuring bridge is of the familiar quadrilateral form,containing in its four main arms the ohmic resistors l, 2, 3, and 4which may consist of required resistance values which can be set bymeans of suitable scales, or thermo-resistors or hot conductors (e.g.,in the case of heating and ventilating regulators), which are adapted toone another in a manner already known per se in the art, in such a waythat in the desired regulated state, equilibrium prevails in the bridgeand there is no difference in potential between the points or junctionsA and B. The bridge is provided with the usual operating current fromthe mains or supply connections 21 and 22, supplying direct current tothe other two corners C and D of the quadrilateral arms.

In the diagonal balancing circuit or bridge circuit between the points Aand B, there is a break-through device 5 which will fire or becomeconductive when subjected to a predetermined difference of potential onopposite sides, and a primary winding 6 of an impulse transformer 7, inseries with the break-through device 5. Also, in parallel with theelements 5 and 6, there is a capacitor 8. Also in parallel with thecapacitor 8 and in parallel with the series connected elements 5 and 6,there is preferably an adjustable resistor 9, which may however beomitted if desired.

The secondary winding of the impulse transformer 7 has a central tap.Circuit conductors go from the central tap and from the respective endsof the secondary winding to the respective diodes l0 and I1, and throughthem to the respective windings l2 and 13 of self-holding relays of theknown type in which, upon actuation of the windings l2 and 13, the relaywill be held closed for a predetermined time interval after current hasceased to flow through the winding 12 or 13. The relays, when closed,will supply operating current from the mains l4 and 15 to the adjustingor regulating motor M to operate the motor in one direction or theother, depending upon which relay is closed. The motor, in turn, adjustsone of the variables of the process or operation which is beingregulated by the present regulator. For example, the motor may move adamper in an opening or closing direction, or adjust a valve, or adjustan electrical resistance.

The operation is as follows: in the balanced state, there is no voltageor difference in potential between the bridge points A and B; thereforethe capacitor 8 has no charge. But when a detuning or imbalance occurs(e.g., in the form of a change in the resistance of the resistor l, or areadjustment of a thermo-resistor or change in the conductivity of oneof the other elements 2, 3, or 4 in the arms of the bridge) then apotential difference will occur between the points A and B, and thecapacitor 8 becomes charged. At the moment when the voltage across thecapacitor has approximately reached the ignition voltage of thebreak-through device 5, this device cuts through or fires, and thecapacitor 8 discharges through the primary winding 6 of the impulsetransformer 7. The impulse produced in the secondary winding of thetransformer is passed through one or the other of the diodes 10 and 11,depending upon the polarity, to operate one or the other of the windingsof the self-holding relays, to switch the motor and of the bridgeresistances. Also, it is influenced by the resistor 9, if such aresistor is included. The lower the resistance of the resistor 9, thelonger it will take the capacitor 8 to become charged sufficiently tooperate the break-through device 5 and activate the transformer 7. Thegreater the degree of imbalance of the bridge, the faster the capacitor8 will become recharged sufficientlyto activate the transformer, and thefaster will be the successive operations of the follow-up motor M. Thusthe regulating apparatus automatically operates at a time sequenceproportional to the degree of detuning or imbalance of the bridge; thegreater the degree or intensity of imbalance, the quicker the successionof the regulating impulses.

The element 5 has been described above merely as a break-through device.A very satisfactory form of such device is a diac, well known in theelectronic field. However, other break-through devices of known kind maybe used, e.g., certain known forms of glow tube, as shown by 5a in FIG.2.

What is claimed is:

l. A pulse generating measuring bridge or the like comprising anelectrical bridge having arms containing resistances at least one ofwhich is responsive to a magnitude to be regulated, a diagonal bridgecircuit connecting two diagonally opposite points of said arms, saiddiagonal bridge circuit including a capacitor charged in response to animbalance producing a difference in potential between said two points, abreakthrough device and an impulse transformer primary winding in serieswith each other and in parallel with said capacitor, said capacitorbeing discharged through said break-through device and said primarywinding to I produce an impulse in a secondary winding of saidtransformer when the charge on said capacitor reaches a threshold valuesufficient to cause firing of said break-through device, said secondarywinding having a central tap, and regulating means operable in responseto an impulse in said secondary winding, said regulating means includingan electric motor for regulating a vari-' able magnitude to which saidelectrical bridge is responsive, a first relay for causing-operation ofsaid motor in a first direction, a second relay for: causing operationof said motor in an opposite direction, and

relay operating circuit connections including a conductor from saidcentral tap to both of said relays, a conductor from one end of saidsecondary winding to said first relay, and a conductor from the oppositeend of said secondary winding to said second relay.

2. A regulator as defined in claim 1, wherein said break-through deviceis a diac.

3. A regulator as defined in claim 1, wherein said break-through deviceis'a glow lamp.

4. A regulator as defined in claim 1, wherein said bridge circuitincludes a resistor in parallel with said capacitor for influencing thetime required for said cagacitor to become charged to said t resholdvalue.

. A regulator as defined in claim wherein said re- UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,699,427 Dated October 171972 Inventor(s) Hermann Friedrich Albrecht et a1 It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

On the cover sheet [73] the name of the assignee should readRollei-Werke Franke G Heidecke Signed and sealed this 1st day of May1973.

(SEAL) Attest: v v

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PO-1050 (10-69) USCOMM-DC 60376-P69 U.S. GOVERNMENTPRINTING OFFICE: 1969 0-366-334.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIQN Patent No. 3,699,427 Dated October 17 1972 Invent0r(s) Hermann Friedrich Albrecht eta1 It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

On the cover sheet [73] the name of the assignee should readRollei-Werke Franke G Heidecke Signed and sealed this lst day of May1973 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GQTTSCHALK Attesting Officer Commissionerof Patents FORM powso H0459) USCOMM-DC scan-pas US. GOVERNMENT PRINTlNGOFFICE: 19.9 0-356-33.

1. A pulse generating measuring bridge or the like comprising anelectrical bridge having arms containing resistances at least one ofwhich is responsive to a magnitude to be regulated, a diagonal bridgecircuit connecting two diagonally opposite points of said arms, saiddiagonal bridge circuit including a capacitor charged in response to animbalance producing a difference in potential between said two points, abreak-through device and an impulse transformer primary winding inseries with each other and in parallel with said capacitor, saidcapacitor being discharged through said break-through device and saidprimary winding to produce an impulse in a secondary winding of saidtransformer when the charge on said capacitor reaches a threshold valuesufficient to cause firing of said break-through device, said secondarywinding having a central tap, and regulating means operable in responseto an impulse in said secondary winding, said regulating means includingan electric motor for regulating a variable magnitude to which saidelectrical bridge is responsive, a first relay for causing operation ofsaid motor in a first direction, a second relay for causing operation ofsaid motor in an opposite direction, and relay operating circuitconnections including a conductor from said central tap to both of saidrelays, a conductor from one end of said secondary winding to said firstrelay, and a conductor from the opposite end of said secondary windingto said second relay.
 2. A regulator as defined in claim 1, wherein saidbreak-through device is a diac.
 3. A regulator as defined in claim 1,wherein said break-through device is a glow lamp.
 4. A regulator asdefined in claim 1, wherein said bridge circuit includes a resistor inparallel with said capacitor for influencing the time required for saidcapacitor to become charged to said threshold value.
 5. A regulator asdefined in claim 4, wherein said resistor in parallel with saidcapacitor is a variable resistor.
 6. A regulator as defined in claim 1,further including a diode in each of said conductors from the ends ofsaid secondary winding to their respective relays.
 7. A regulator asdefined in claim 1, wherein each of said relays is a self-holding relayremaining closed for a predetermined time interval after termination ofan impulse which has served to close the relay to operate said motor.